The long term goal of this project is to use structure-based drug design methodologies to develop a non-hormonal male contraceptive. To be a good target for the development of a male contraceptive, a molecule needs to be both essential for the formation of a functional spermatozoon and solely present in germ cells. To this end we have identified and characterized a multi-functional DNA and RNA-binding protein, contrin, that abundant in the testis and appears specific to germ cells. Contrin is the mammalian homologue of FRG Y2 well defined germ cell proteIn originally characterized in Xenopus oocytes that functions as both a transcription factor and a regulator of translation. Contrin plays an important role In the translational repression of stored l.e., "paternal" mRNA in mammalian male germ cells and also functions as a DNA-binding protein with activity as a transcription factor. The germ cell specificity and the critical functions played by this multifunctional DNA and RNA-binding protein during spermatogenesis make contrin an attractive, novel, and realistic target for male contraceptIon. To reach our goal to effectively suppress spermatogenesis and only spermatogenesis with a drug that blocks one or more of the functions of contrin, it is necessary to demonstrate first that spermatogenesis is disrupted when contrin does not function. To accomplish this, the following is proposed: In Specific Aim 1, we shall isolate cDNAs encoding mouse and human contrin to define contrin expression In mammals. In Specific Aim 2, we shall determine the importance and specificity of contrin to spermatogenesis by functionally knocking out the contrin gene using homologous recombination. This will confirm that male sterility is achieved without other discernible phenotypic changes. In Specific Aim 3, contrin will be synthesized in an expression vector. This will allow us to use contrin in "in vitro" transcriptional assays and for 3-dimensional structure analyses by X-ray crystallography. The structural studies will allow us to utilize combinatorial chemistry to develop specific non-peptide inhibitors of contrin function.